Field of the Invention
The present invention relates to an apparatus for measuring a water quality, and more particularly, to a pen type of apparatus for measuring multiple water qualities, which is capable of measuring acidity (pH) and electric conductivity (EC) without interfering with each other in agricultural water for hydroponic cultivation to easily confirm the measured results.
Description of the Related Art
The contamination of water today caused by municipal sewage and industrial wastewater not only destroys ecosystems, but is becoming a serious social concern by causing the depletion of water for industry and agriculture and water resources needed for drinking water. For example, while underground water is still clean, thoughtless development is leading to its accelerated depletion and contamination.
Recently, however, as awareness has gradually grown on the importance of managing and using water resources, various management systems for preventing the contamination of water resources and efficiently using them are being developed and implemented, so that water resources can not only be used for industry, but for household drinking water and water for living, and various other uses.
Meanwhile, modern living environments are becoming increasingly eco-friendly, whereby hydroponic techniques are becoming widespread in many households which directly cultivate hydroponic plants indoors such as immature stemmed plants or organic vegetables, and small fruit-bearing plants, and various types of household aquariums are being installed to control indoor temperature and humidity. In such cases, the individual households need to be supplied with water with a suitable level of quality for raising the hydroponic plants or the aquarium fish, and users need to personally manage the water to maintain it in an optimal state.
That is, in order to provide suitable growing conditions for a normal household to cultivate hydroponically or keep an aquarium, the quality of water used for this purpose must be continuously measured and managed in terms of water level, temperature, acidity, and electric conductivity (EC). It is particularly important that water used for hydroponics or an aquarium be measured and managed in terms of acidity (pH or hydrogen ion concentration) and EC or Total Dissolved Solids (TDS) characteristics. To this end, various types of water quality measuring devices have been disclosed so as to be easily used even by normal households. For example Korean Registered Patent No. 10-0874779 (Cited Patent Document 1) discloses a hydrogen ion concentration measuring device, and Korean Registered Patent No. 10-0865639 (Cited Patent Document 2) discloses an electric conductivity measuring device.
Also, multipurpose water quality measuring devices have recently been introduced that can measure both acidity and electric conductivity. FIG. 1 is a schematic perspective view illustrating the general structure of a multipurpose water quality measuring device according to the related art, which was developed by the present applicant. As illustrated, a water quality measuring device 10 of the related art is configured of a bar-shaped housing 11 having a predetermined length, a measuring unit 12 provided on one side of the housing 11, and a display unit 13 and a user input unit 14 provided on an outer surface of the housing 11. A protective cap 15 for protecting a sensor of the measuring unit 12 is provided on one side of the housing. Also, while not shown, a control unit for measuring and displaying acidity and electric conductivity is provided together with a power supply unit within the housing 11.
While various methods may be employed for measuring acidity and electric conductivity using a multipurpose water quality measuring device, in general, a method is used of taking measurements using a voltage that is output according to changes in the hydrogen ion concentration inside and outside a hydrogen sensitive glass bulb, and for electric conductivity, a technique is used in which a current is applied between positive and negative electrodes and the resistance that occurs across a solution in the water being measured is used. To this end, the measuring unit 12 provided on one side of the water quality measuring device 10 is configured of a pH sensor electrode 12a for measuring acidity, an EC sensor electrode 12b for measuring electric conductivity, and a temperature sensor 12c for measuring the temperature of the water being measured.
While such a water quality measuring device has the advantage that one device may be used to measure both acidity and electric conductivity, it involves the limitation that the pH sensor electrode 12a and the EC sensor electrode 12b are disposed close together so that interference occurs between the two sensor electrodes. Specifically, when the pH sensor electrode 12a and the EC sensor electrode 12b are immersed in the same water being measured, both sensor electrodes simultaneously contact the water being measured and cause interference therebetween.
In detail, the pH sensor electrode 12a is configured of a measuring electrode within the glass bulb and a reference electrode outside the glass bulb, and measurements are taken by discharging a flow of an electrolyte solution such as potassium chloride (KCl) from the reference electrode. At this point the potassium chloride flowing out from the pH sensor electrode 12a side is dissolved in the water being measured and changes the resistance of the water being measured so that an inaccurate value is measured by the EC sensor electrode 12b when the electric conductivity is measured.
Additionally, when the water quality measuring device is stored, the pH sensor electrode 12a needs to always be maintained in a state of wet contact with the electrolyte solution (KCl), while the EC sensor electrode, on the other hand, 12b needs to be kept in a clean state. Thus, when the electrolyte solution on the pH sensor electrode 12a side contacts the EC sensor electrode 12b and contaminates the EC sensor electrode 12b, the inconvenience arises of having to wash the EC sensor electrode 12b for each use in order to maintain the clean state thereof and produce accurate electric conductivity measurements.